The present invention relates to an apparatus suitable for carrying out the production of carbon black. In another aspect, the invention relates to a process for the production of carbon black.
At the present time, the principal use for carbon black is as a reinforcing agent for rubber. Large amounts are utilized in the manufacture of vehicular tires. Carbon black strengthens tires into which it has been compounded, thus lessening the probability of untimely tire failure. Additionally, the incorporation of carbon black into vehicular tires and other rubber goods increases their useful life.
Carbon blacks which impart improved properties to rubber goods, particularly greater strength and longer life, are much sought after. It has recently been found that carbon blacks produced in vortex flow, oil furnace reactors which have a wide distribution in aggregate particle sizes impart improved resilience, lower hysteresis and better wire cord adhesion to rubber into which it has been compounded than conventional blacks, which have a narrower distribution in aggregate particle sizes.
Tint residual, which is a calculated property of carbon black made by a vortex flow, oil furnace process, is reflective of the distribution of the aggregate sizes in a carbon black sample, as compared to the average distribution and aggregate sizes of blacks commercially available from Phillips Petroleum Company and others manufacturing carbon black by vortex flow, oil furnace type processes. Tint residual is the difference between the tint observed during testing of carbon black sample and the tint which would be expected from the sample because of its surface area and structure. Tint residual is given by the equation: EQU TR=T-[56.0+1.057(CTAB)-0.002745(CTAB).sup.2 -0.2596[C-DBP]-0.201(N.sub.2 SA-CTAB)]
In this formula the abbreviations used have the following meanings and the properties are measured as described:
TR: Tint residual PA1 CTAB: The specific surface area of the carbon black sample measured as described in ASTM D 3765-79, meter.sup.2 /gm. PA1 N.sub.2 SA: The surface area of the carbon black sample measured using nitrogen in accordance with the ASTM method D-3037-76, meter.sup.2 /gm. PA1 C-DBP: The structure of the compressed carbon black sample measured as described in ASTM D 3493-76, cc/100 grams. PA1 T: The tint or tinting strength of the carbon black sample measured in accordance with ASTM 3265-76, assigning reference black IRB No. 4 the value of 100.
A carbon black sample which is characterized by a negative tint residual has a relatively broad distribution in aggregate sizes while a carbon black sample characterized by a positive tint residual has a relatively narrow distribution of particle sizes. Normally, the tint residual exhibited by a carbon black sample will be between about -20 and +20, commercially available blacks having a tint residual between about-2 and +15, usually between about 0 and +5.
The tint exhibited by a carbon black sample is dependent upon, among other things, the size of the particles in the sample as well as on the size distribution of the particles making up the sample. Tint calculated from the CTAB, N.sub.2 SA, and C-DBP values obtained from a sample, as in the bracketed portion of the above equation, fails to fully account for the size distribution of the particles. The tint residual of the sample, the difference between the observed tint and calculated tint, is caused largely by the particle size distribution in the sample and thus can be employed to yield useful information.
For a carbon black characterized by a given surface area and structure, it would be highly desirable to minimize the tint exhibited by the sample, because the low tint would be indicative of a wide distribution of particle size. Conversely, for a carbon black sample exhibiting a given tint, it would be highly desirable to increase the average surface area of the particles.
Heretofore, carbon black having a broad distribution of aggregate sizes had been produced successfully only in small reactors. The reactors which had been successfully employed to produce this special kind of carbon black were extremely sensitive to changes in operating conditions, and thus tricky to operate. Additionally, the production of broad distribution particle size carbon black by a battery of small reactors would be frequently economically unattractive. A commercial reactor capable of producing carbon black having a tint residual of less than for example, -5 or -6, would be extremely desirable.